title: Decomplexification in critical illness and injury: relationship between heart rate variability, severity of illness, and outcome.
abstract: OBJECTIVE
  To determine if decomplexification of heart rate dynamics occurs in critically ill and injured pediatric patients. We hypothesized that heart rate power spectra, a measure of heart rate dynamics, would inversely correlate with measures of severity of illness and outcome.
  
  
  METHODS
  A prospective clinical study.
  
  
  METHODS
  A 12-bed pediatric intensive care unit (ICU) in a tertiary care children's hospital.
  
  
  METHODS
  One hundred thirty-five consecutive pediatric ICU admissions.
  
  
  METHODS
  None.
  
  
  RESULTS
  We compared heart rate power spectra with the Pediatric Risk of Mortality (PRISM) score, the Pediatric Cerebral Performance Category (PCPC), and the Pediatric Overall Performance Category (POPC). We found significant negative correlations between minimum low-frequency and high-frequency heart rate power spectral values recorded during ICU stay and the maximum PRISM score (log low-frequency heart rate power vs. PRISM, r2 = .293, p < .001; and log high-frequency heart rate power vs. PRISM, r2 = .243, p < .001) and outcome at ICU discharge (log low-frequency heart rate power vs. POPC or PCPC, r2 = .429, p < .001; and log high-frequency heart rate power vs. POPC or PCPC, r2 = .271, p < .001).
  
  
  CONCLUSIONS
  Our data support the hypothesis that measures of heart rate power spectra are inversely related and negatively correlated to severity of illness and outcome in critically ill and injured children. The phenomenon of decomplexification of physiologic dynamics may have important clinical implications in critical illness and injury.
authors.affiliation: Department of Pediatrics, University of Rochester School of Medicine, NY, USA.
authors.forename: B
authors.initials: B
authors.lastname: Goldstein
authors.forename: D H
authors.initials: DH
authors.lastname: Fiser
authors.forename: M M
authors.initials: MM
authors.lastname: Kelly
authors.forename: D
authors.initials: D
authors.lastname: Mickelsen
authors.forename: U
authors.initials: U
authors.lastname: Ruttimann
authors.forename: M M
authors.initials: MM
authors.lastname: Pollack
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D016638:Critical Illness / Q000628:therapy*; D004562:Electrocardiography / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D006339:Heart Rate; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D011446:Prospective Studies; D012720:Severity of Illness Index; D012815:Signal Processing, Computer-Assisted; D016896:Treatment Outcome